ST. LOUIS -- After struggling in their last two games coming up with big hits, the Mets hoped to get a jolt from their offense as they opened a three-game series against the Cardinals on Friday night.

Pete Alonso delivered.

Alonso homered, collected two hits and scored twice in the Mets’ 5-4 win. And that home run may have been one of the unlikeliest in MLB this season.

The Mets’ No. 1 prospect per MLB Pipeline drove a 97 mph fastball from Ryan Helsley 432 feet, per Statcast, to center field for his seventh home run of the season. The pitch was low and out of the zone and likely would have been ball four, but Alonso clubbed it 112 mph into the grassy knoll at Busch Stadium.

Alonso said he was in survival mode with the count full.

“That was kind of my two-strike approach to cut down my swing a little bit and hit the ball where it’s pitched,” Alonso said. “Thankfully, the guy on the mound was throwing cheeseballs up there, I think he was at 98, 99 [mph] tonight, and he supplied the power for me and I just took a nice easy swing and thankfully I caught it on the sweet spot and it went for me.”

It may not have been the hardest home run the Mets’ slugger has hit this season -- he had a 118 mph homer at Atlanta on April 11 -- but it may have been the most impressive.

All seven of Alonso’s homers this season have come against relievers, and this was the first to come before the seventh inning.

“I’m just being the same guy from the first at-bat to the last one,” Alonso said. “Let’s say if I don’t have success early in the game, I don’t want to let that carry into the next at-bat or into the field. I want to stay the same Pete Alonso inning one through inning nine, and keeping a neutral attitude throughout the game, I think I can definitely attribute that to having success.”

The homer gave the Mets a seemingly comfortable 5-1 lead. It turned out to be the decisive run.

“He just grinds out every at-bat, and if somebody makes a mistake, it seems like he hits it hard,” Mets manager Mickey Callaway said. “That pitch was 97 [mph], and it went out a little harder than that. He continues to impress everybody.”

Robinson Cano also had a big night, collecting three hits, including a pair of doubles, with an RBI and a run scored. J.D. Davis doubled home a run and reached base three times, as the Mets finished with 11 hits, reaching double-digits in a game for a Major League-high 13th time this season.

Improvement for Vargas, strong showing for 'pen

Mets starter Jason Vargas pitched only four innings, but he allowed only one run. It was a far cry from his last outing, in which he lasted one-third of an inning and gave up four runs.

“I think that my changeup was quite a bit better tonight, as far as the depth of it,” Vargas said. “Those first couple of innings, I was kind of missing my arm slot a little and getting myself into some counts that would have been better to be ahead in, but my changeup had a lot better depth tonight.”

After Vargas' departure, Seth Lugo pitched two innings of relief to earn the win and Robert Gsellman bailed New York out of a tough situation in the eighth with runners on the corners and one out, retiring Jedd Gyorko and Matt Carpenter.

“That’s going to give him [Gsellman] a lot of confidence,” Callaway said. “Obviously, a big spot, he came in and he made some quality pitches in a situation that was tough. We have all the faith in the world in him. His stuff is nasty, and he’s going to get it going and this is going to help.”

Edwin Diaz pitched a scoreless ninth, recording his seventh save of the season and converting his 17th straight save opportunity dating back to last season.